Hydroxy-functionalized polyoxyalkylene ether compositions derived from ring-opening polymerization of epoxides have long been known to be materials which are directly useful as surfactants, functional fluids, and the like or which may be readily reacted further to provide polyurethanes, fuel additives, and the like. However, such compositions have generally been regarded as susceptible to thermal and/or oxidative degradation when exposed to high temperatures and air for prolonged periods of time. This lack of stability, which is particularly pronounced when the composition is prepared using an epoxide wherein at least one of the carbon atoms in the oxirane ring bears both a carbon and a hydrogen substitutent (as in propylene oxide, 1,2-butylene oxide, cis-2,3-butylene oxide, or trans-2,3-butylene oxide), has discouraged the use of such compositions in certain end-use applications requiring good thermal or oxidative resistance such as fuel detergent additives. Since the aforementioned epoxides which in theory could be used to manufacture compositions of this type are relatively inexpensive as compared to other polymerizable monomers, however, it would be highly desirable to develop hydroxy-functionalized polyoxyalkylene ether compositions based on such substituted epoxides which have improved heat- and/or air-tolerance.